Ink-jet head

ABSTRACT

An ink-jet head comprises a joint member having an ink outlet port out of which ink supplied from an ink supply source flows, and a passage unit having an ink receiving port that receives the ink flowing out of the ink outlet port of the joint member. A filter is disposed within a first ink passage inside the passage unit. The first ink passage extends in the same direction as an ink flow direction from the ink outlet port to the ink receiving port. In the first ink passage of the passage unit, a first space is formed between the ink receiving port and the filter, and a second space is formed contiguous to the first space with the filter interposed between the first and second spaces within the first ink passage. The cross-sectional shape and size of each space in a direction perpendicular to an ink flow direction are constant along the ink flow direction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ink-jet head in which an ink passagehas a filter therein.

2. Description of Related Art

An ink-jet recording apparatus that ejects ink to form an imagecomprises an ink-jet head having many nozzles for ejecting ink and alsohaving therein ink passages that lead to the nozzles. The ink-jet head,having an ink receiving port for receiving ink from an ink tank, isconnected to the ink tank via a tube, etc., so that ink may be suppliedfrom the ink tank through the ink receiving port into the head.

In such a tube-connection type head, in general, a joint member isdisposed between the ink receiving port and the tube. In a knowntechnique, for example, a joint member has two conical membersconfronting each other on their open bottoms to define therein twofunnel shaped spaces, and a filter for removing dust contained in ink isdisposed between the two funnel shaped spaces (see U.S. PatentApplication Publication No. 2002-196318).

In this technique, an ink passage formed by the two funnel shaped spacesbecomes relatively larger at its portion around the filter. With thisconfiguration, flow velocity and pressure of ink fall around the filter,to often generate bubbles resulting from air contained in ink. Thebubbles may hinder ink flow through the filter, enter an ink passage ofthe head to deteriorate election performance, and, in the worst case,cause failure of ink ejection.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an ink-jet head capableof suppressing generation of bubbles around a filter.

A continued study by the present inventors has revealed that theforegoing object can be achieved by properly defining configurations ofspaces that are formed on upstream and downstream sides of a filterdisposed within an ink passage.

According to a first aspect of the present invention, there is providedan ink-jet head comprising a joint member, a passage unit, and a filter.The joint member has an ink outlet port out of which ink supplied froman ink supply source flows. The passage unit has a layered structure ofa plurality of sheet members. The passage unit includes an ink receivingport that confronts the ink outlet port and receives the ink flowing outof the ink outlet port, and an ink passage that extends from the inkreceiving port in a layered direction of the sheet members andsubsequently extends in a plane direction of the sheet members that isperpendicular to the layered direction. The filter is disposed in aportion of the ink passage extended in the layered direction. The inkoutlet port has a smaller area than the ink receiving port, the jointmember has a flat face that confronts the passage unit and surrounds theink outlet port. In the portion of the ink passage extended in thelayered direction, a straight columnar space is formed between the inkreceiving port and the filter, and another straight columnar space isformed between the filter and one of the sheet members on a downstreamside of the filter.

In the aforementioned construction, straight columnar spaces are formedbetween the ink receiving port and the filter, and between the filterand one of the sheet members on a downstream side of the filter, in theportion of the ink passage extended in the layered direction. As aresult, ink that flows from the ink outlet port of the joint memberthrough the ink receiving port of the passage unit into the ink passagein the passage unit is hardly decreased in flow velocity and pressurearound the filter. Therefore, since air contained in ink is unlikely todevelop into bubbles, generation of bubbles around the filter can besuppressed.

According to a second aspect of the present invention, there is providedan ink-jet head comprising a joint member, a passage unit, and a filter.The joint member has an ink pathway through which ink supplied from anink supply source passes, an ink outlet port formed at one end of theink pathway, and a space which is formed in the vicinity of the one endof the ink pathway and whose cross-sectional shape and size in adirection perpendicular to an ink flow direction toward the ink outletport are constant along the ink flow direction. The passage unit has aplurality of nozzles that eject ink, an ink receiving port that islarger than the ink outlet port and receives the ink flowing out of theink outlet port, a first ink passage that has, at one end thereof, theink receiving port and extends in the same direction as the ink flowdirection toward the ink outlet port, and a second ink passage thatextends from the other end of the first ink passage to the nozzles. Thepassage unit is connected to the joint member such that the inkreceiving port confronts the ink outlet port. The filter is disposedwithin the first ink passage of the passage unit. A first space isformed between the ink receiving port and the filter. A cross-sectionalshape and size of the first space in the direction perpendicular to theink flow direction are constant along the ink flow direction. A secondspace is formed on a downstream side of the filter within the first inkpassage. A cross-sectional shape and size of the second space in thedirection perpendicular to the ink flow direction are constant along theink flow direction. The first space and the second space are contiguousto each other with an interposition of the filter.

In the aforementioned construction, the space whose cross-sectionalshape and size in the direction perpendicular to the ink flow directionare constant along the ink flow direction is formed in the vicinity ofone end of the ink pathway of the joint member at which the ink outletport is provided. In addition, within the first ink passage of thepassage unit, the first space and the second space contiguous to eachother are formed on upstream and downstream sides of the filter with thefilter interposed therebetween. Each of the first and second spaces hascross-sectional shape and size in the direction perpendicular to the inkflow direction, which are constant along the ink flow direction. As aresult, ink that flows from the ink outlet port of the joint memberthrough the ink receiving port of the passage unit into the first inkpassage is hardly decreased in flow velocity and pressure around thefilter. Therefore, similar advantage to that of the above-mentionedfirst aspect can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

Other and further objects, features and advantages of the invention willappear more fully from the following description taken in connectionwith the accompanying drawings in which:

FIG. 1 is an exploded perspective view of an ink-jet head according to afirst embodiment of the present invention;

FIG. 2 is an exploded perspective view of a passage unit included in theink-jet head of FIG. 1;

FIG. 3 is a partial enlarged perspective view of the passage unit ofFIG. 2;

FIG. 4 is a sectional view around one longitudinal end of the passageunit of FIG. 1, illustrating the passage unit and a joint memberdisposed on the passage unit;

FIG. 5 is a partial enlarged perspective view of a passage unit includedin an ink-jet head according to a second embodiment of the presentinvention;

FIG. 6 is a sectional view around one longitudinal end of the passageunit of FIG. 5, illustrating the passage unit and a joint memberdisposed on the passage unit;

FIG. 7 is a partial enlarged perspective view of a passage unit includedin an ink-jet head according to a third embodiment of the presentinvention; and

FIG. 8 is a sectional view around one longitudinal end of the passageunit of FIG. 7, illustrating the passage unit and a joint memberdisposed on the passage unit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some preferred embodiments of the present invention will hereinafter bedescribed with reference to the accompanying drawings.

First, an ink-jet head according to a first embodiment of the presentinvention will be described with reference to FIGS. 1, 2, 3, and 4. Asillustrated in FIG. 1, an ink-jet head 1 of this embodiment comprises apassage unit 30, an actuator unit 20, and a flexible printed circuit(FPC) 10, all of which have substantially rectangular planar shapes. Thepassage unit 30, the actuator unit 20, and the FPC 10 are put in layersin their thickness direction.

The actuator unit 20 serves to change the volume of later-describedpressure chambers 48 (see FIGS. 2 and 3) of the passage unit 30. The FPC10 serves to feed a drive signal to the actuator unit 20. As will bedescribed later, many nozzles 41 (see FIGS. 2 and 3) are formed on aface of the passage unit 30 opposite to its face having the actuatorunit 20 layered thereon, i.e., on a lower face thereof that is not shownin FIG. 1. As the actuator unit 20 changes the volume of the pressurechambers 48, the ink is ejected through the nozzles 41.

The actuator unit 20 includes, for example, a plurality of piezoelectricsheets (not illustrated) of flat-plate shape spanning later-describedmany pressure chambers 48 (see FIGS. 2 and 3) of the passage unit 30; acommon electrode (not illustrated) that is disposed between thepiezoelectric sheets, shared by the many pressure chambers 4B, and keptat the ground potential; and individual electrodes (not illustrated)disposed at positions corresponding to the respective pressure chambers48. Voltage application via the FPC 10 to between the common electrodeand the individual electrodes causes distortion of the piezoelectricsheet sandwiched between these electrodes, so that the volume of thepressure chambers 48 of the passage unit 30 can selectively be changed.Ink is consequently ejected through the corresponding nozzles 41 of thepassage unit 30,

As shown in FIGS. 2 and 3, the passage unit 30 has a layered structureof seven metal sheets of substantially rectangular shape, i.e., a nozzleplate 31, a spacer plate 32, three manifold plates 33, 34 and 35, a baseplate 36, and a cavity plate 37. As the plates 31 to 37, there may beadopted, for example, plates of Ni—Fe alloy with a thickness ofapproximately 40 to 150 μm, in which formed are many openings orrecesses by means of stamping or etching. The plates 31 to 37 are bondedto one another with an adhesive applied on each plane such that theopenings or recesses may communicate with each other.

In the nozzle plate 31, many nozzles 41 each having a minute diameterare formed at a fine pitch in a staggered pattern along two parallelreference lines 31 a and 31 b that extend in a lengthwise direction ofthe nozzle plate 31. The nozzle 41 has, for example, a tapered shape,and ink is ejected from a tip end thereof.

Many holes 42 corresponding to the respective nozzles 41 are formed inthe spacer plate 32.

In the three manifold plates 33, 34, and 35, formed are many holes 43,44, and 45 corresponding to the respective nozzles 41 as well asmanifold channels 53, 54, and 55 that extend along a lengthwisedirection of the plates. The manifold channels 53, 54, and 55 are formednear both widthwise sides of the plates. When the manifold plates 33 to35 are put in layers, the manifold channels 53, 54, and 55 are unitedwith each other in a layered direction to form ink passages that extendalong a plane of the passage unit 30.

Many holes 46 corresponding to the respective nozzles 41 and many holes47 are formed in the base plate 36. The many holes 47 aligned along alengthwise direction are provided near both widthwise sides of theplate, Two substantially circular openings 56 are formed near onelengthwise end of the base plate 36. The two openings 56 are arranged inparallel along a width of the plate, A diameter of each opening 56 isalmost the same as a width of the vicinity of one end of the manifoldchannels 53, 54, and 55. The openings 56 communicate with one end of themanifold channels 53, 54, and 55.

Filters 60 are so disposed on the base plate 36 as to cover the tworespective openings 56. The filters 60 have a function of removing dust,etc., contained in ink. Each filter 60 has a substantially circularshape with a diameter larger than that of the opening 56 and with athickness of approximately 50 to 75 μm.

In the cavity plate 37, many pressure chambers 48 are formed at adistance from each other in two lines on opposite sides of a centerlinethat is along a lengthwise direction of the plate. Each pressure chamber48 is formed penetrating through the cavity plate 37 in a thicknessdirection by means of stamping, and arranged such that its length may,in a plan view, be in parallel with a width of the cavity plate 37. Whenreference lines 37 a and 37 b (see FIG. 3) parallel to the centerline ofthe cavity plate 37 are defined on opposite left and right sides of thecenterline along the lengthwise direction of the cavity plate 37, eachpressure chamber 48 arranged on the right side of the centerline has onelengthwise end thereof positioned on the reference line 37 a that isdefined on the left side of the centerline, and each pressure chamber 48arranged on the left side of the centerline has one lengthwise endthereof positioned on the reference line 37 b that is defined on theright side of the centerline. In addition, the pressure chambers 48 areso arranged that lengthwise centerlines of the pressure chambers 48arranged in two lines may alternate with each other in the lengthwisedirection of the cavity plate 37. That is, the pressure chambers 48 arearranged in a staggered pattern.

As shown in FIG. 3, an end 48 a of each pressure chamber 48 nearer thecenter of the cavity plate 37 communicates through the holes 46, 45, 44,43, and 42 with the nozzle 41. On the other hand, the other end 48 b ofeach pressure chamber 48 is formed in a recessed manner by means of halfetching so that it may open only on a lower face side of the cavityplate 37. The other end 48 b communicates through the hole 47 with themanifold channels 53, 54, and 55.

Moreover, two substantially circular openings 57 arranged parallel in awidthwise direction are formed at such positions near one lengthwise endof the cavity plate 37 as to correspond to the respective openings 56 ofthe base plate 36. Portions of the openings 57 on an upper face side ofthe cavity plate 37 serve as ink receiving ports 57 a. A diameter ofeach opening 57 is larger than that of the opening 56 of the base plate36 and almost the same as that of the filter 60, so that the filter 60may fit in the opening 57 when the cavity plate 37 is put on an upperface of the base plate 36 (see FIG. 4). Since the cavity plate 37 isthicker than the filter 60, an upper face of the cavity plate 37 ispositioned above an upper face of the filter 60, as illustrated in FIG.4.

As illustrated in FIGS. 2 and 4, a first ink passage and a second inkpassage are formed inside the passage unit 30. The first ink passage hasthe ink receiving port 57 a arranged at one end thereof, and extends ina thickness direction of the plates 31 to 37 (i.e., in a direction of anarrow y in FIG. 4). The second ink passage extends from the other end ofthe first ink passage to the nozzle 41. More specifically, the first inkpassage is made up of the ink receiving port 57 a, the openings 57 and56, and portions of the manifold channels 53, 54, and 55 opposing theopening 56. The second ink passage is made up of the manifold channels53, 54, and 55 except for their portions opposing the opening 56, thehole 47, the pressure chamber 48, the holes 46, 45, 44, 43, and 42, andthe nozzle 41.

Ink supplied into the passage unit 30 firstly passes through the firstink passage, i.e., through the ink receiving port 57 a, the openings 57and 56, and one end of the manifold channels 53, 54, and 55. Then, theink flows within the manifold channels 53, 54, and 55 in theirlengthwise direction, to be distributed, through the hole 47, among therespective pressure chambers 48. The ink reserved in the respectivepressure chambers 48 reach the nozzles 41 through the holes 46, 45, 44,43, and 42.

The filter 60 is, as illustrated in FIG. 4, disposed in the opening 57in the course of the first ink passage within the passage unit 30 so asto be slightly spaced from the ink receiving port 57 a on a downstreamside.

Next, with reference to FIG. 4, a description will be given to a jointmember 70 arranged on the passage unit 30. FIG. 4 illustrates a sectionof a portion corresponding to only one of the two ink receiving ports 57a (see FIG. 2).

The joint member 70 has a substantially cylindrical shape with asubstantially column-shaped ink pathway 72. The ink pathway 72 has, atone end thereof nearer the passage unit 30, an ink outlet port 72 a ofsubstantially circular shape that has a smaller diameter than that ofthe ink receiving port 57 a. The joint member 70 is disposed on thepassage unit 30 such that the ink outlet port 72 a may confront the inkreceiving port 57 a.

The other end (not illustrated) of the ink pathway 72 of the jointmember 70 is connected to, for example, one end of a tube having theother end thereof connected to an ink tank as an ink supply source. Inksupplied from the ink tank flows through the tube into the ink pathway72 of the joint member 70, and then through the ink outlet port 72 ainto the ink receiving port 57 a of the passage unit 30.

Since the ink pathway 72 of the joint member 70 has a substantiallycolumnar shape, the ink pathway 72 has, in the vicinity of one endthereof, a space V3 whose cross-sectional shape and size in a directionperpendicular to an ink flow direction toward the ink outlet port 72 a(i.e., in a direction of an arrow x in FIG. 4) are constant along theink flow direction (i.e., along the direction of the arrow y in FIG. 4).A cross-section of the space V3 in the direction of the arrow x has acircular shape with a smaller diameter than those of both the openings57 and 56 of the passage unit 30.

A flange portion 71 is formed around one end of the joint member 70having the ink outlet port 72 a provided thereat, and an outer diameterof the one end is larger than that of the ink receiving port 57 a. Anend face of the joint member 70 at the above-mentioned one end, i.e., aface thereof confronting the passage unit 30 is flat. An adhesive andthe like is applied to an outer periphery of this face which is thenbrought into contact with a circumference of the ink receiving port 57 aof the passage unit 30, so that the passage unit 30 and the joint member70 are secured to each other.

Between the ink receiving port 57 a and the filter 60, formed is a firstspace V1 in a straight columnar shape whose cross-sectional shape andsize in the direction of the arrow x in FIG. 4 are constant along thedirection of the arrow y. A length of the first space V1 in thedirection of the arrow y, that is, a distance between the upper face ofthe filter 60 and the ink receiving port 57 a is approximately 50 μm.

On the other hand, a second space V2 is Formed on the downstream side ofthe filter 60 (downstream in the direction of the arrow y) within thefirst ink passage. The second space V2 is contiguous to the first spaceV1 with an interposition of the filter 60. Similarly to the first spaceV1, the second space V2 is in a straight columnar shape and has itscross-sectional shape and size in the direction of the arrow x constantalong the direction of the arrow y. However, its length in the directionof the arrow y, that is, a distance between a lower face of the filter60 and an upper face of the spacer plate 32 is larger than that of thefirst space V1.

As shown in FIG. 4, the flat face of the joint member 70 confronting thepassage unit 30, the filter 60, and the spacer plate 32 are parallel toeach other.

As described above, in the ink-jet head 1 according to the firstembodiment of the present invention, the space V3 whose cross-sectionalshape and size in the direction of the arrow x are constant along thedirection of the arrow y is formed in the vicinity of one end of the inkpathway 72 of the joint member 70 at which the ink outlet port 72 a isprovided (see FIG. 4). In addition, formed within the first ink passageof the passage unit 30 are the first and second spaces V1 and V2 whoserespective cross-sectional shapes and sizes in the direction of thearrow x are constant along the direction of the arrow y. The first andsecond spaces V1 and V2 are provided on upstream and downstream sides ofthe filter 60, respectively, to be contiguous to each other. As aresult, ink that flows from the ink outlet port 72 a of the joint member70 through the ink receiving port 57 a of the passage unit 30 into thefirst ink passage is hardly decreased in flow velocity and pressurearound the filter 60. Therefore, since air contained in ink is unlikelyto develop into bubbles, generation of bubbles around the filter 60 canbe suppressed. Further, this suppression of generation of bubbles canprevent deterioration in ejection performance, and moreover malfunctionssuch as failure of ink ejection.

Besides, a distance between the ink receiving port 57 a and the filter60 is shorter than a distance between the filter 60 and the spacer plate32 on the downstream side of the filter 60. In other words, the firstspace V1 is shorter in the direction of the arrow y than the secondspace V2. Thereby, the flow velocity and pressure of ink are furtherprevented from decreasing on the upstream side around the filter 60 andparticularly within the first space V1. Thus, generation of bubbleswithin the first space V1 is less likely to occur. Even if bubbles aregenerated, their growth is suppressed. Consequently, deterioration inejection performance and, further, malfunctions such as failure of inkejection, which result from bubbles, can effectively be suppressed.

Further, the passage unit 30 has a layered structure of a plurality ofplates 31 to 37, with which the first and second spaces V1 and V2 can beformed into predetermined shapes with more ease and at a lower cost ascompared with, e.g., a resin-molded passage unit.

The filter 60 is so disposed on, among the plurality of plates 31 to 37,the base plate 36 as to cover the opening 56, and the cavity plate 37 tobe put immediately on the base plate 36 has the opening 57 into whichthe filter 60 is fitted. In this case, by, e.g., setting thicknesses ofthe filter 60 and the cavity plate 37 at predetermined values, the firstspace V1 of very small length in the direction of the arrow y can beformed accurately and easily.

Next, an ink-jet head according to a second embodiment of the presentinvention will be described with reference to FIGS. 5 and 6.

The ink-jet head according to the second embodiment comprises anactuator unit 20, an FPC 10, and a joint member 70, all of which are thesame as those of the aforementioned first embodiment, and a passage unit130 that differs from the passage unit 30 of the first embodiment. Thesame members as in the first embodiment will be denoted by the samereference numerals, and a description thereof will be omitted.

As seen from FIGS. 2 and 5, the passage unit 130 of this embodiment isdifferent from that of the first embodiment in, among the seven plates,third and fourth plates from an upper side, and the other plates 31 to33, 36, and 37 are the same as those of the first embodiment.

As illustrated in FIG. 5, differently from the first embodiment, a thirdplate 135 has holes 147 that correspond to the holes 47 formed in thebase plate 36, instead of the manifold channels 55 (see FIG. 2). Inaddition, two substantially circular openings 158 are formed at suchpositions near one lengthwise end of the plate 135 as to correspond tothe respective openings 56 of the base plate 36. A diameter of eachopening 158 is almost the same as that of the opening 56 of the baseplate 36.

In a fourth manifold plate 134, on the other hand, manifold channels 154that extend along a lengthwise direction of the plate are formed nearboth widthwise sides of the plate. These manifold channels 154 are,however, shorter in the lengthwise direction than the manifold channels54 (see FIG. 2) of the first embodiment. More specifically, one end ofeach manifold channel 154 does not reach a position opposing the opening56 formed in the base plate 36. Two substantially circular openings 159are formed in the manifold plate 134 at such positions near theabove-mentioned one end as to correspond to the openings 56 of the baseplate 36. A diameter of each opening 159 is smaller than that of theopening 56 of the base plate 36 and that of the opening 158 of the plate135, and also than a width of the vicinity of one end of the manifoldchannel 53 formed in the lower manifold plate 33. Each opening 159communicates with one end of the corresponding manifold channel 53.

A first ink passage inside the passage unit 130 is made up of the inkreceiving port 57 a, the openings 57, 56, 158, and 159, and a portion ofthe manifold channel 53 opposing the opening 56. A second ink passage ismade up of the manifold channel 53 except for its portion opposing theopening 56, the manifold channel 154, the holes 147 and 47, the pressurechamber 48, the holes 46, 45, 44, 43, and 42, and the nozzle 41.

In this embodiment, as illustrated in FIG. 6, a hole (i.e., the hole159) corresponding to the first ink passage and formed in the manifoldplate 134 spaced from the filter 60 on the downstream side is smallerthan holes (i.e., the holes 56 and 158, and one end of the manifoldchannel 53) corresponding to the first ink passage and formed in theother plates 36, 135, and 33 located downstream of the filter 60.Accordingly, the opening 159 functions as a flow regulator. The flowregulator formed by the opening 159 is located at a downstream end of asecond space V2 a. More specifically, an interval between a lower faceof the filter 60 and an upper face of the manifold plate 134 having theopening 159 is formed as the second space V2 a.

As described above, in the ink-jet head according to the secondembodiment of the present invention, the flow regulator is formed by theopening 159 at the downstream end of the second space V2 a, on thedownstream side of the filter 60 in the first ink passage. Therefore,flow velocity and pressure of ink are increased around the opening 159and particularly within the second space V2 a, so that generation ofbubbles is less likely to occur. Even if bubbles are generated, theirgrowth is suppressed. Accordingly, deterioration in ejection performanceand, further, malfunctions such as failure of ink ejection, which resultfrom bubbles, can effectively be suppressed.

An ink-jet head according to a third embodiment of the present inventionwill then be described with reference to FIGS. 7 and 8.

The ink-jet head according to the third embodiment comprises an actuatorunit 20, an FPC 10, and a joint member 70, all of which are the same asthose of the aforementioned first embodiment, and a passage unit 230that differs from the passage units 30,130 of the first and secondembodiments. The same members as in the first and second embodimentswill be denoted by the same reference numerals, and a descriptionthereof will be omitted.

As seen from FIGS. 2 and 7, the passage unit 230 of this embodiment isdifferent from that of the first embodiment in, among the seven plates,first, third, and fourth plates from an upper side. The other plates 31to 33, and 36 are the same as those of the first embodiment. A thirdplate 135 is the same as that of the second embodiment.

As illustrated in FIG. 7, a first cavity plate 237 has, near onelengthwise end thereof, two substantially circular openings 257. Adiameter of each opening 257 is smaller than that of the opening 57 ofthe first embodiment, and almost the same as that of the opening 56 ofthe base plate 36. Portions of the openings 257 on an upper face side ofthe cavity plate 237 serve as ink receiving ports 257 a.

On the other hand, a fourth manifold plate 234 has, similarly to themanifold plate 134 of the second embodiment, the manifold channels 154and the holes 44 formed therein. The fourth manifold plate 234 also hastwo substantially circular openings 259 formed at such positions nearone end thereof as to correspond to the openings 56 of the base plate36. A diameter of each opening 259 is larger than that of the opening159 of the second embodiment, and each opening 259 communicates with oneend of each manifold channel 53. More specifically, as illustrated inFIG. 8, the opening 259 is larger than any of the holes formed in theother plates and constituting a first ink passage (i.e., than any of theopening 257 of the cavity plate 237, the opening 56 of the base plate36, and one end of the manifold channel 53 of the manifold plate 33).

The first ink passage inside the passage unit 230 is made up of the inkreceiving port 257 a, the openings 257, 56, 158, and 259, and a portionof the manifold channel 53 opposing the opening 56. A second ink passageis made up of the manifold channel 53 except for its portion opposingthe opening 56, the manifold channel 154, the holes 147 and 47, thepressure chamber 48, the holes 46, 45, 44, 43, and 42, and the nozzle41.

The third embodiment differs from the first and second embodiment alsoin the location of filters 260. Each filter 260 of this embodiment is,differently from those of the first and second embodiments, not disposedon the base plate 36, but disposed on the manifold plate 33 and withinthe opening 259 of the manifold plate 234 such that the filter 260 maycover the vicinity of one end of the manifold channel 53. As a result, afirst space V1 b is formed longer in a direction of an arrow y than asecond space V2 b. In other words, the filter 60 is, in the first andsecond embodiments, disposed nearer to the ink receiving port 57 a thanto the spacer plate 32, while, in this embodiment, the filter 260 isdisposed nearer to the spacer plate 32 than to the ink receiving port257 a.

In this embodiment, unlike the first and second embodiments, a diameterof the first ink passage is unchanged through the upstream anddownstream of the filter 260.

As described above, in the ink-jet head according to the thirdembodiment of the present invention, a distance between the inkreceiving port 257 a and the filter 260 is longer than a distancebetween the filter 260 and the spacer plate 32 on a downstream side ofthe filter 260. In other words, the first space V1 b is longer in thedirection of the arrow y than the second space V2 b. Therefore, flowvelocity and pressure of ink are further prevented from decreasing onthe downstream side around the filter 260 and particularly within thesecond space V2 b. Thus, generation of bubbles within the second spaceV2 b is less likely to occur. Even if bubbles are generated, theirgrowth is suppressed. Consequently, deterioration in ejectionperformance and, further, malfunctions such as failure of ink ejection,which result from bubbles, can effectively be suppressed.

The filter may not necessarily be disposed on the base plate 36 as inthe first and second embodiments or on the manifold plate 33 as in thethird embodiment but may be disposed at various positions, as long asthose positions are within the first ink passage of the passage unit. Byvariously changing the location of the filter, the first and secondspaces formed on upstream and downstream sides of the filter can bechanged in configuration and in size.

The filters 60 or 260 are put in position by being fitted in the opening57 of the cavity plate 37 in the first and second embodiments or bybeing fitted in the opening 259 of the manifold plate 234 in the thirdembodiment. However, this is not limitative, and the filter can be putin position by means of other approaches. Moreover, it is not necessaryto form the filter 60 or 260 into a separate member from the cavityplate 37 or the manifold plate 234. For example, many pores thatfunctions as the filter 60 or 260 can be formed in the plate 37 or 234.

Further, as to the first and second spaces in the first ink passage ofthe passage unit 30, the second space is longer in the ink flowdirection in the first and second embodiment, and the first space islonger in the ink flow direction in the third embodiment. However, thefirst and second spaces may have substantially the same length in theink flow direction.

Still further, in the first to third embodiments, the passage unit has alayered structure of a plurality of sheet members. However, this is notlimitative, and the passage unit may be formed by, e.g., resin-molding,etc.

An application of the ink-jet head according to the present invention isnot limited to printers, but also to, for example, ink-jet typefacsimiles or copying machines.

While this invention has been described in conjunction with the specificembodiments outlined above, it is evident that many alternatives,modifications and variations will be apparent to those skilled in theart. Accordingly, the preferred embodiments of the invention as setforth above are intended to be illustrative, not limiting. Variouschanges may be made without departing from the spirit and scope of theinvention as defined in the following claims.

1. An ink-jet head comprising: a joint member having an ink pathwaythrough which ink supplied from an ink supply source passes, an inkoutlet port formed at one end of the ink pathway, and a space which isformed in the vicinity of the one end of the ink pathway and whosecross-sectional shape and size in a direction perpendicular to an inkflow direction toward the ink outlet port are constant along the inkflow direction; a passage unit having a plurality of nozzles that ejectink, an ink receiving port that is larger than the ink outlet port andreceives the ink flowing out of the ink outlet port, a first ink passagethat has, at one end thereof, the ink receiving port and extends in thesame direction as the ink flow direction toward the ink outlet port, anda second ink passage that extends from the other end of the first inkpassage to the nozzles, the passage unit being connected to the jointmember such that the ink receiving port confronts the ink outlet port;and a filter disposed within the first ink passage of the passage unit,wherein: a first space is formed between the ink receiving port and thefilter, a cross-sectional shape and size of the first space in thedirection perpendicular to the ink flow direction being constant alongthe ink flow direction; a second space is formed on a downstream side ofthe filter within the first ink passage, a cross-sectional shape andsize of the second space in the direction perpendicular to the ink flowdirection being constant along the ink flow direction; and the firstspace and the second space are contiguous to each other with the filterinterposed therebetween, wherein the first space is greater in thex-direction than the second space.
 2. The ink-jet head according toclaim 1, wherein the first space is shorter in the ink flow directionthan the second space.
 3. The ink-jet head according to claim 1, whereina flow regulator is formed on the downstream side of the filter withinthe first ink passage, and is located at a downstream end of the secondspace.
 4. The ink-jet head according to claim 1, wherein: the passageunit has a layered structure of a plurality of sheet members with holesformed therein, the holes constituting the plurality of nozzles, the inkreceiving port, the first ink passage, and the second ink passage; thefilter is disposed at a position, on one of the plurality of sheetmembers, to cover a hole formed in the one sheet member andcorresponding to the first ink passage; and a second sheet member putimmediately on the sheet member on which the filter is disposed has ahole in which the filter is fitted.
 5. The ink-jet head according toclaim 1, wherein: the passage unit has a layered structure of aplurality of sheet members with holes formed therein, the holesconstituting the plurality of nozzles, the ink receiving port, the firstink passage, and the second ink passage; the filter is disposed at aposition, on one of the plurality of sheet members, to correspond to thefirst ink passage; and a hole corresponding to the first ink passage andformed in another one of the sheet members spaced from the filter on thedownstream side is smaller than other holes corresponding to the firstink passage and formed in other sheet members.
 6. An ink-jet headcomprising: a joint member having an ink pathway through which inksupplied from an ink supply source passes, an ink outlet port formed atone end of the ink pathway, and a space which is formed in the vicinityof the one end of the ink pathway and whose cross-sectional shape andsize in a direction perpendicular to an ink flow direction toward theink outlet port are constant along the ink flow direction; a passageunit having a plurality of nozzles that eject ink, an ink receiving portthat is larger than the ink outlet port and receives the ink flowing outof the ink outlet port, a first ink passage that has, at one endthereof, the ink receiving port and extends in the same direction as theink flow direction toward the ink outlet port, and a second ink passagethat extends from the other end of the first ink passage to the nozzles,the passage unit being connected to the joint member such that the inkreceiving port confronts the ink outlet port; and a filter disposedwithin the first ink passage of the passage unit, wherein: a first spaceis formed between the ink receiving port and the filter, across-sectional shape and size of the first space in the directionperpendicular to the ink flow direction being constant along the inkflow direction; a second space is formed on a downstream side of thefilter within the first ink passage, a cross-sectional shape and size ofthe second space in the direction perpendicular to the ink flowdirection being constant along the ink flow direction; and the firstspace and the second space are contiguous to each other with the filterinterposed therebetween, wherein the first space is longer in the inkflow direction than the second space.